The invention relates to an X-ray source that includes a liquid metal target and an electron source for the emission of an electron beam in a window of a duct section wherethrough the liquid metal target flows in the operating condition, and also to an X-ray apparatus that is provided with such an X-ray source.
An X-ray source of this kind is known from DE 198 21 939.3. The window that is traversed by the electrons from the electron source so as to be incident on the liquid metal target is then cooled by a turbulent flow of the target. This type of cooling significantly enhances the continuous loadability of the X-ray source. A further increase of the loadability, however, is opposed by the fact that the window as well as the areas of the X-ray source that enclose the window, that is, the window frame, are subject to comparatively high thermal stresses. The origins of such stresses lie in the development of heat that is due notably to the direct incidence of electrons of high energy and the flow of the hot liquid metal underneath the window. Furthermore, the scattered electrons that exhibit only a small loss of energy also contribute to the development of heat.
This is particularly critical because the connection between the window and the window frame can withstand a limited maximum temperature only that is dependent on the bond technology used (for example, soldering, gluing).
Therefore, it is an object of the present invention to provide an X-ray source that has a liquid metal target and an electron source of the kind set forth and whose continuous loadability can be further increased.
This object is achieved by means of an X-ray source of the kind set forth which, as disclosed in claim 1, is characterized in that the duct section is formed by a first duct segment that includes the window and wherethrough the liquid metal target flows, as well as by a second duct segment wherethrough a cooling medium flows and which is connected to the first duct segment in such a manner that the area in which the electron beam acts on the first duct segment is cooled.
A particular advantage of this solution consists in the fact that the increased dissipation of heat enables a further increase of the loadability of the X-ray source, that is, notably in the case of applications where a high X-ray dose must be generated within a short period of time, for example, in CT apparatus with a high scanning rate.
The dependent claims relate to advantageous further embodiments of the invention.
The claims 2 to 5 disclose steps that realize a further improvement of the dissipation of heat in various manners. In the embodiments that are disclosed in the claims 6 and 7 the duct section is advantageously configured in such a manner that on the one hand an X-ray beam that propagates at a given spatial angle of aperture is not disturbed while on the other hand it is not necessary either to tolerate any influencing of the cooling.